A touch panel is a device in which a sensor for touch operation detection (touch panel sensor) is overlaid on the upper surface of a display device (displaying device) such as a liquid crystal panel and in which two functions of display and input are united. In the touch panel, when an operator performs a touch operation to a display on the screen, information of the operated position is output outside as a signal and an external device conducts a suitable action desired by the operator based on the information of the operated position.
Owing to such advantages that it is easy to handle because its operation is intuitively easy to understand and that it is capable of being miniaturized because an input device and a display device can be integrated without any keyboard, a tough panel has been widely used for ATM in banks, ticket vending machines in stations, information terminals in libraries, copying machines, car navigation systems, mobile phones, personal digital assistants, portable game machines, facsimile machines, and the like.
There are various detection types for the touch operation in a touch panel. For example, there are a resistive film type, an electrostatic capacitance type, and the like and the electrostatic capacitance type also includes a surface electrostatic capacitance type, a projection electrostatic capacitance type, and the like. Among these, the projection electrostatic capacitance type with which multi-touch and a gesture operation are possible has been widely used for mobile phones, tablet PC's, and the like.
In the projection electrostatic capacitance type touch panel sensor, when a user touches a screen, a change in electrostatic capacitance between an electrode and another electrode is detected to detect a touched position.
Here, the touch panel sensor has an electrode in an X-axis direction (hereinafter sometimes referred to as an X-side electrode) and an electrode in a Y-axis direction (hereinafter sometimes referred to as a Y-side electrode) and a position in the X direction is detected by the X-side electrode and a position in the Y direction that is orthogonal to the X direction is detected by the Y-side electrode. Then, a two-dimensional touch position is specified by the X-side electrode and the Y-side electrode.
In conventional touch panel sensors, a transparent ITO (Indium Tin Oxide) electrode is used as an electrode but the electrode has problems that it exhibits a high resistance value and is not suitable for a large-sized panel.
In the case of the ITO electrode, there is also a problem of high costs.
Accordingly, in recent years, attention is focused on a metal electrode that is formed by arranging extra-fine metal lines in a grid pattern. This metal electrode has such various advantages that it can be applied to a large-sized panel owing to its small resistance value and high sensitivity, that a life of a battery can be enhanced because its consumption of electric power is little, that it costs low, and the like.
However, on the other hand, in the case of the metal electrode using the metal lines, since the metal lines are not transparent and has metallic luster, there is a problem that light from the outside reflects by the metal lines and thus visibility for the display part is decreased by the reflected light.
Conventionally, the following have been considered and proposed as measures against the problem.
For example, Patent Document 1 discloses an invention of a “touch panel sensor” and also discloses that a metal electrode formed on a surface of a transparent substrate is constituted by a metal wiring part of cupper or the like and a low reflective layer containing fine particles of carbon black or the like and that the metal wiring part and the low reflective layer are formed by an inkjet method.
However, in the case where the low reflective layer is formed by an inkjet method, it is difficult to thin the line width and there is a concern that visibility for the display part may decrease when the line width becomes thick.
Moreover, there is no structure proposed in Patent Document 1 that is capable of reducing the reflection of the light from the outside of a viewing side even in the case where the laminated body composed by laminating the transparent substrate and the metal electrode is reversed upside down.
On the other hand, Patent Document 2 discloses an invention of a “laminated body” and discloses that a laminated body composed by laminating a conductive metal layer on a transparent substrate is constructed as a blackened layer, a metal layer, a substrate, a blackened layer, and a metal layer in this order from a viewing side, and that copper nitride in an already oxidized state is formed as the blackened layer by reactive sputtering.
However, as for the technique in which copper nitride is formed by reactive sputtering as a blackened layer as described in Patent Document 2, the effect of reducing reflectance by the blackened layer is not necessarily satisfactory and there is a concern that visibility may decrease.
Patent Document 2 discloses two cases where the blackened layer is provided on the surface opposite to the substrate, of the metal layer that forms an electrode and where the blackened layer is provided between the substrate and the metal layer. However, in both cases, reflection in specific one direction is only prevented and the laminated body does not have a structure that is capable of reducing the reflection of the light from the outside of a viewing side also in the case where the laminated body is reversed upside down.
Patent Document 1: JP-A-2013-235315
Patent Document 2: JP-A-2013-169712